A mixed reality surgery is known as a surgical method that is used by a surgeon to perform a surgical operation on a patient (for example, see Non-Patent Document 1). According to this surgical method, a surgeon performs a surgical operation in a situation where images of blood vessels and organs are projected onto the body surface of a patient by a projector. By using images that are projected onto the body surface of a patient in such a manner, the surgeon can grasp the position of the organ that is to be subjected to a surgical operation, in advance of the surgical operation. Therefore, the surgeon can more accurately and more easily perform a surgical operation on the patient.